1. Field of the Invention
The present invention relates to an image pickup apparatus capable of performing tracking control, such as a video camera and a digital still camera.
2. Description of the Related Art
Many inner focus type image pickup apparatuses can perform tracking control that moves a correction lens group such as a focus lens group to correct image plane variation caused due to variation of magnification performed by moving a magnification-varying lens group. The tracking control enables zooming, that is, variation of magnification with keeping an in-focus state. The tracking control performs position control of the correction lens group in response to the movement of the magnification-varying lens group by using tracking data indicating a positional relationship of the magnification-varying lens group and the correction lens group, the tracking data being prestored in a memory.
However, even if the position control of the correction lens group is performed according to the tracking data, defocusing may be caused due to errors in shape and dimension of each lens group and an attachment error of an image sensor such as a CCD sensor for photoelectrically converting an object image.
Japanese Patent Laid-Open No. 8-220414 discloses an image pickup apparatus that acquires positions of the correction lens group optimum for positions of the magnification-varying lens group where defocusing can be reduced, and thereby performs adjustment of the tracking data (hereinafter referred to as “tracking adjustment”). Moreover, Japanese Patent Laid-Open No. 11-183775 discloses an image pickup apparatus that calculates a difference between ideal tracking data and actually measured tracking data, and performs tracking adjustment by using the difference as adjustment data.
Furthermore, some recent image pickup apparatuses can move the image sensor in an optical axis direction during the variation of magnification to achieve a higher magnification than that of the image pickup apparatus moving only the magnification-varying lens group while reducing an apparatus size. Such image pickup apparatuses perform the tracking control for the image sensor as well as for the correction lens group, and also need the tracking adjustment for the image sensor.
However, the necessity of the tracking adjustment for the image sensor in addition to that for the correction lens group makes the tracking adjustment in the entire image pickup apparatus complex.